1. Field of the Invention
The present invention relates to an apparatus and method for determining whether or not a motor lock error occurs in a sensorless motor, and more particularly to an apparatus and method for determining the presence or absence of a motor lock error in a sensorless BLDC (Blushless DC) motor using the magnitude of a current applied to the sensorless BLDC motor when determining a position and speed of the sensorless BLDC motor on the basis of the magnitudes of current and voltage signals applied to the sensorless BLDC motor.
2. Description of the Related Art
FIG. 1 is a block diagram illustrating a conventional sensorless motor drive system.
Typically, a motor comprised of a rotor and a stator determines a position and speed of the rotor to normally operate the rotor, and controls a voltage and current applied to the motor on the basis of the determined position and speed, such that it is able to control the rate of rotation of the rotor. Specifically, a method for mounting a sensor to the motor to determine the position and speed of the rotor has been widely used. The sensor mounted to the motor recognizes a rotation state of the motor at intervals of a predetermined time, determines a phase of the motor, detects the speed of the motor, and determines the presence or absence of a motor lock error in the motor, such that it can properly cope with a faulty operation of the motor.
However, the above-mentioned motor drive method for detecting the phase and speed of the motor using the sensor, and normally operating the motor on the basis of the detected phase and speed of the motor has a disadvantage in that it unavoidably increases the costs of production and the size of a circuit, and is unable to correctly recognize a rotation state of the motor when the sensor is damaged, so that it can correct the faulty operation of the motor.
Therefore, there has recently been widely used a sensorless motor drive system capable of detecting a position signal of the motor using voltage and current signals, instead of using the sensor. Operations of the above-mentioned sensorless motor drive system will hereinafter be described with reference to FIG. 1.
As shown in FIG. 1, the conventional sensorless motor drive system includes a rectifier unit 10 and an inverter unit 20. The rectifier unit 10 includes an AC power source; and a diode for receiving an AC voltage from the AC power source, and half-wave-rectifying the received AC voltage to a DC voltage. The inverter unit 20 includes six power components, each of which receives a voltage from a capacitor in which a voltage rectified by the rectifier unit 10 is charged, converts the received voltage into a three-phase AC voltage, and outputs the three-phase AC voltage to a motor 30.
The above-mentioned sensorless motor drive system includes a main controller 40 and a gate signal processor 50. The main controller 40 includes a position detector 41 for detecting a voltage and current transmitted from the inverter unit 20 to the motor 30, calculating a rotor position on the basis of the detected voltage and current, and generating a position detection signal; and a speed controller 42 for determining a voltage of each phase so as to allow the motor 30 to be optimally operated by the position detection signal generated from the position detector 41, and generating a control signal. The gate signal processor 50 receives the output signal from the speed controller 42, and converts the received signal into a potential capable of being used as an input signal of each power component.
According to operations of the above-mentioned conventional sensorless motor drive system, the rectifier unit 10 rectifies an AC input voltage to a DC voltage, the rectified voltage is charged in the capacitor, and is converted into a three-phase AC voltage by the inverter unit 20 comprised of 6 power components. The three-phase AC voltage is received in the motor 30 so that the rotor of the motor 30 is rotated.
The inverter unit 20 is controlled by the control signal generated from the main processor 40. The main processor 40 includes the position detector 41 and the speed controller 42 so as to optimally operate the motor. The position detector 41 detects voltage and current signals applied to the motor 30, detects a rotor position of the motor 30, and transmits a position detection signal.
The speed controller 42 determines and outputs voltages of individual phases using the position detection signal so that a current suitable for the rotor position flows in the motor 30. The gate signal processor 50 receives the output signal from the speed controller 42, and converts the received signal into a potential capable of being used as an input signal of each power component contained in the inverter unit 20.
According to the above-mentioned conventional art, a rotor position and rotation rate of the sensorless motor can be detected without using the sensor so that the operation of the rotor is corrected so as to allow the motor to be optimally operated. However, if a motor lock error unexpectedly occurs in the above-mentioned sensorless motor, there is no solution capable of correcting the motor lock error in the sensorless motor drive system.
In more detail, provided that a motor lock error occurs because a rotor is rotated at a rate less than a normal rotation rate even though a current flows in the motor, the position of the rotor is erroneously calculated, and each phase voltage flowing in the motor is abnormally controlled by the erroneously-calculated rotor position, so that an overcurrent flows in the motor. Particularly, if the motor lock error is generated when the motor is mounted to a washing machine, an overcurrent flows in the motor, so that a temperature of the motor is increased and the motor or overall system is damaged.
Also, if a washing machine capable of preventing the motor lock error from being generated to solve the above-mentioned problem of the damage of the motor or system detects the motor lock error, it includes a means for compulsorily turning off a power source applied to the washing machine itself, instead of including a means for correcting the motor lock error to perform a normal washing mode, so that the washing mode is not fully performed and incompletely terminated, resulting in greater inconvenience of users.